Non-aqueous amine systems have been suggested as energy-efficient alternatives to conventional aqueous amine systems in post-combustion carbon capture, as low regeneration temperatures can be achieved. The solubility of CO2 and heat of absorption in non-aqueous systems were studied using the sterically hindered amine 2-amino-2-methyl-1-propnaol (AMP) in the organic solvent dimethyl sulfoxide (DMSO). 13C NMR was used to study the product species in solution as CO2 reacts with AMP in either DMSO or N-methyl-2-pyrrolidone (NMP). The solubility of CO2 in AMP/DMSO showed that low loadings could be achieved at 80–88 °C, indicating that regeneration can be carried out at lower temperatures than in conventional aqueous systems. Precipitation occurred at 25 wt% AMP in DMSO, increasing the overall capacity of the system. The heat of absorption decreased with increasing temperature, and was explained by physical absorption dominating the absorption mechanism at higher temperatures. This was also confirmed by the results of NMR, as less chemically absorbed species were observed at higher temperatures. The reaction products observed in AMP/DMSO and AMP/NMP were identified as the AMP carbamate, bicarbonate from water impurities, and the AMP carbonate from CO2 reacting with the hydroxyl group of AMP.
- Heat of absorption